DE3103963A1 - Process for preparing cyanogen chloride - Google Patents

Description

Dipl.-Ing. F. A. Weιckmann, Dipl.-Chem. B. Huber Dr. Ing.H. Liska

8000 MUNICH 86, DEN H / SM / Hl POSTBOX 860 820

MÖHLSTRASSE 22, CALL NUMBER 98 39 21/22

SKW Trostberg Aktiengesellschaft

Process for the production of cyanogen chloride

The invention relates to the preparation of cyanogen chloride by thermal decomposition of cyanuric chloride.

Cyanogen chloride is an important reagent in the synthesis of organic compounds such as pharmaceuticals, sweeteners and pesticides etc.

The preparation of cyanogen chloride is generally carried out by Chlorination of hydrogen cyanide according to the equation

HCN + Cl ₉ ■■ ClCN + HCl.

This representation is made more difficult not only by the problematic one Availability of the raw materials, but also through the disposal required for reasons of environmental protection the resulting highly diluted hydrochloric acid.

• · I

Due to the formation of sodium chloride contaminated with cyanide, the reaction is aqueous sodium cyanide solution not suitable with chlorine.

The cyanogen chloride production described in DE-PS 24 42 161 according to the equation

(CN) ₉ + ri 2C1CN

do £ t V ^

has the disadvantage that dicyan is difficult to access.

The object of the invention was therefore to provide an economical process for avoiding the disadvantages described Production of cyanogen chloride to provide.

This object is solved by a method for the production of cyanogen chloride by thermal decomposition of cyanuric chloride of an activated carbon catalyst in a reversal of the formation reaction, which is characterized in that the cyanuric chloride to at 480-800 ⁰ C heated activated carbon is depolymerized.

The trimerization of cyanogen chloride to cyanuric chloride over an activated carbon catalyst is known and is described, for example, in DE-PS 833 490. It is a Gleicbgewichtsreaktion, wherein the equilibrium lies in temperature ranges between 350 and 400 ⁰ C almost completely on the side of the cyanuric chloride. If the temperature rises further, the starting products regress. However, chlorine and dicyan are increasingly formed during this process.

It has now surprisingly been found that the formation of chlorine and dicyan in the thermal decomposition of cyanuric chloride can largely suppress if one works according to the process according to the invention.

Preferably, the temperature of the active carbon is 580 to 680 ⁰ C and in particular 620 to 68O ⁰ C. This gives the cyanogen chloride substantially free of contaminants, particularly free of HCN. The cyanuric chloride vapor is preferably passed over the activated carbon catalyst in such an amount that there is a ratio of 0.6 to 0.7 1 catalyst per 1 kg of cyanogen chloride formed. The reaction time (contact time of the cyanuric chloride with the catalyst) is preferably 10 to 40 s, and for practical reasons in particular 1o to 2ο s.

A quartz tube or graphite tube is preferably used as the reactor containing the activated carbon. The heating of the reactor is advantageously carried out in three successive zones, and expediently electrically. Through this can be the actual reaction zone, which is supplied with the main heat must be optimally heated without overheating the reaction equilibrium in the subsequent zone is adversely affected.

The cyanuric chloride is fed to the reactor containing the activated carbon, preferably in a continuous manner and the reaction gas is continuously removed and worked up. The unreacted cyanuric chloride contained in the reaction gas and the chlorine and dicyan formed during the reaction are expediently circulated in the reactor, depending on Intermittent or continuous operation, fed back in.

A particular advantage of the process according to the invention is that it can be carried out without a solvent; thereby contains the arising Cyanogen chloride does not have any moisture that would interfere with its further processing.

An expedient, suitable for the industrial scale implementation of the process is shown in the drawing using the Flow sheet (Fig. 1) explained in more detail.

From the storage container A, in the simplest case a delivery container, powdered cyanuric chloride is introduced into the melting container B in portions via a lock. The melting vessel is (indirectly) heated electrically (direct) or by means of thermal oil at temperatures above the melting point of the cyanuric chloride (15O ⁰ C). The melt is continuously withdrawn from the melt container with the aid of a metering pump with a heatable pump head and pressed into the evaporation pot C. The heat of evaporation is supplied by electrical heating of the floor. The rising cyanuric chloride vapor reaches the reactor D, which is charged with activated carbon and which is electrically heated from the outside in three successive zones. A thermocouple that can be moved in the longitudinal guide in the center of the catalyst bed enables the conversion zone to be precisely detected and then the temperature to be set externally by means of appropriate heat regulation. The reaction gas leaving the top of the reactor · Omit about 500 ⁰ C and is cooled down in the further line at about 200 ⁰ C. The unreacted cyanuric chloride, about 7% of the initial amount, is _{removed from the gas flow in two parallel-connected, alternatively working separators E 1} and E- and fed back to the evaporator pot C, via conventional dust filters, e.g. made of ceramic material, the cyanogen chloride, which still contains proportions of chlorine and dicyan, fed to the separating column F. The top of the column is provided with a cooling unit, where the enriched at a temperature of 5 ⁰ C and cyanogen chloride and upward escaping gas from the residual ·: free cyanogen chloride. In the bottom of the column, cyanogen chloride is obtained with a purity of over 99%. While the dicyan / chlorine mixture is returned to the evaporator pot C, the cyanogen chloride obtained can be in liquid form

♦ ♦ ·

Further use or can be obtained in gaseous form via an evaporator at 13 ^{° C.}

The following examples show the dependence of cyanogen chloride formation (yield and purity) on the residence time (Contact time) and the reaction temperature.

example 1

A quartz tube of 50 cm length and 10 cm ² cross section was filled with 60, 90, 120, 150 and 180 cc of activated carbon, and passed a constant current of cyanuric chloride vapor at 600 ⁰ C. The reaction products were ^{freed from unreacted cyanuric chloride in a downstream separator made of glass, cooled to 16 °} C., and this was determined by weight at the end of each experiment. The percentages, like the dicyano and cyanogen chloride contents in the reaction gas, relate to the cyanuric chloride used.

Dwell time
S. not implemented
Cyanuric chloride
Wt% Dicyan
Wt% Cyanogen chloride
Wt% 15th 10.0 5.0 78.5 20th 7.5 3.5 83.7 25th 5.5 3.0 87.4 30th 4.5 3.0 91.4 35 2.5 3.0 93.5 40 1.5 3.0 94.0

The difference to 100% is in each case chlorine, which is formed in a stoichiometric ratio to dicyan.

Example 2

Through a graphite tube filled with activated carbon, cyanuric chloride vapor was in a
Amount passed, which corresponded to a residence time of 15 s. As described in Example 1, the contents of unreacted cyanuric chloride, dicyan and cyanogen chloride were determined. In the table below, the percentages are based on the cyanuric chloride used.

temperature
⁰ C not implemented
Cyanuric chloride
Wt% Dicyan
Wt% Cyanogen chloride
Wt% 560 24.3 4.3 65.4 580 13.0 4.5 76.4 600 9.0 4.8 79.7 620 5.8 5.1 83.1 640 3.2 5.4 84.0 660 1.8 5.6 85.0

Claims (9)

Patent Attorneys DfpLt-lNG.'H * ^ eic'rwawn, Dipl.-Phys. Dr. K. Fincke Dipl.-Ing. F. A-Weickmann, Dipl.-Chem. B. Huber Dr. Ing. H. Liska 8000 MÜNCHEN 86, DEN '»C Γοι, loo <POSTFACH86O82O ^ & Feb. 1981 MÖHLSTRASSE 22, RUFNUMMUR 98 39 21/22 SKW 220 SKW Trostberg Aktiengesellschaft Dr.-Albert-Frank-Straße 32 D-8223 Trostberg Process for the production of cyanogen chloride patent claims 1. Process for the production of cyanogen chloride by thermal Decomposition of cyanuric chloride on an activated carbon catalyst in reverse of the formation reaction, characterized in that the cyanuric chloride on ^{depolymerized to 480-800 0} C heated activated carbon
will. 2. The method according to claim 1, characterized in that the temperature of the activated carbon
Is 68O ⁰ C - 580th 3. The method according to claim 1 or 2, characterized in that the cyanuric chloride at 0.6-0.71
Catalyst per kg of cyanogen chloride formed is implemented. 4. The method according to any one of claims 1 to 3, characterized
marked that the contact time of the cyanuric chloride with the catalyst is 10 to 20 s. 5. The method according to any one of claims 1 to 4, characterized It is noted that the activated carbon containing reactor is a quartz tube. 6. The method according to any one of claims 1 to 4, characterized in that the activated carbon containing reactor is a graphite tube. 7. The method according to any one of claims 1 to 6, characterized in that the reactor in three successive zones is heated. 8. The method according to any one of claims 1 to 7, characterized in that the cyanuric chloride fed to the reactor containing the activated carbon in continuous operation and the reaction gas continuously is discharged and worked up. 9. The method according to any one of claims 1 to 8, characterized characterized in that unreacted cyanuric chloride and chlorine formed in the reaction and dicyan are fed back into the reactor.